Automatic jack rafter bevel square



Jan. 25, 1944.

P. F. WITTER AUTOMATIC JACK RAFTER BEVEL SQUARE Filed July 27, 1945 Fig.1.

.4 INVENTOR. PH/LHNDER E w/rrse I I arrbiazvers Patented Jan. 25, 1944 UNITED STATES PATENT OFFICE AUTOMATIC JACK RAFTER BEVEL SQUARE Philander F. Witter, Kentfield, Calif.

Application July 27, 1943, Serial No. 496,368

4 Claims.

The present invention relates to improvements in an automatic jack rafter bevel square and it consists of the combinations, constructions and arrangements hereinafter described and claimed.

In the building of a roof, it is necessary that the carpenter cut the ends of the jack rafters at a particular angle so that these ends will fit the hip rafter. The usual practice is to take the right angle carpenters square and lay it on the jack rafter in such a position that the two arms of the square will rest on the side of the rafter. If the angle of the jack rafter is such that there will be a rise of six inches for every twelve inch run, the right square is laid on the rafter so that one arm will measure twelve inches from one edge of the rafter and the other arm will measure six inches from the same edge. A line is drawn on the rafter along the short six inch arm and this line will indicate the angle of the rise out.

The square is now laid on top of the rafter so that one arm will measure thirteen and one-half inches and the other arm will measure twelve inches. The thirteen and one-half inch arm is lined up with the rise out line already made so that a line drawn on the rafter top and along the long square arm will give the proper angle for the side out. The bevel squares are now set for the two angularly disposed rise cut and side out lines and the carpenter can cut al1 of the jack rafter ends at the same angles for the particular roof section being built.

The principal object of my invention is to do line to be drawn on the jack rafter without any previous measurements being made. A quadrant scale is used for indicating the number of inches run and the number of inches rise desired on the jack rafter. The instrument may be set for'the particular run and rise desired and the lines drawn on the jack rafter. The lines will be at the required angles so that the cut jack rafter wil1 fit into place properly.

A further object of my invention is to provide a device of the type described that has foldable parts thus permitting the device to be folded into a compact bundle when not in use and placed in a pocket of the carpenters overalls. The device is simple in construction and is designed to be used to draw lines on jack rafters that after being out, are to be placed on both sides of the hip raften' quadrant.

Other objects and advantages will appear in the following specification, and the novel features of the device will be particularly pointed out in the appended claims.

My invention is illustrated in the accompanying drawing forming a part of this application, in which:'

Figure l is a perspective view of the device shown applied to a jack rafter for the purpose of marking cutting lines on the top and side of the rafter;

Figure 2 is a plan view of the device with the parts folded together;

Figure 3 is a side elevation of Figure 2; Figure 4 is an end view of Figure 2; and Figure 5 is a schematic view illustrating a hip rafter with two jack rafters extending therefrom.

While I have shown only the preferred form of my invention, it should be understood that various changes or modifications may be made within the scope of the appended claims without departing from the spirit and scope of the invention.

In carrying out my invention I provide a jack rafter bevel square that has a body member A which is substantially T-shaped in cross section. The sides of the member A are beveled, as indicated at I in Figure 4. The body A carries two spaced quadrants 2, that are disposed near the head 3, of the body and are arranged on either side of a central web 4, that extends longitudinally throughout the length of the body. Figure 4 indicates that the bases of the quadrants are flanges 5 that extend outwardly and rest on the top of the body A. Rivets B or other suitable fastening means secure the flanges to the body.

Each quadrant has an opening I therein and a pin 8 extends through the aligned openings for pivotally connecting an arm B to the base A. The arm may be locked in various angular positions by a bolt 9 and a butterfly nut H). The bolt 9 moves in an arcuate slot ll, provided in each The ends of the quadrants nearest the head 3 are reinforced and held in spaced relation by an insert 12 that is placed between the quadrants and is secured thereto by rivets It will be noted from Figures 1, 2 and 3 that the arm B carries a stub shaft or pivot pin I4 near its free end. Brackets I 5 are carried by the arm B and have openings l6 for receiving the ends of the shaft [4. The ends of the pin project beyond the outer surfaces of the bracket I 5 for a purpose hereinafter described.

The head 3 on the body A is wedge-shaped, as shown in Figures 1 and 4. The head has two rectangularly-shaped recesses l1 and I8 whose planes extend at right angles with respect to each other. Pivoted arm l9 aud 20 are received in the recesses and swing about screws 2|, that are mounted in the head 3 and pass through openings in the arms I9 and 20. The screws 2| exert sufficient friction on the arms l9 and 20 to hold them in the position into which they are swung. When using the device, either the arm [9 or the arm 20 is opened, this depending upon whether a right hand or a left hand jack rafter is being out.

From the foregoing description of the various parts of the device, the operation thereof may be readily understood.

In Figure 5 I indicate a hip rafter C and a right and a left hand jack rafter D. It is necessary to make a side out on the jack rafter at 22, see Figure 5, and a rise cut on the same rafter at 23. Figure 1 illustrates a perspective view of the jack rafter D with the top of the rafter in dicated at 24- and the side at 25. The carpenter determines what run and rise are desired and adjusts the arm B on the quadrant 2 for this purpose. The quadrant 2 has markings thereon, certain of these being numbered 6, 12 and 18 as indicated at 26. The arm B is swung so that its center will coincide with the mark desired. For example: the mark 18 stands for an eighteen inch rise for every twelve inch run; the mark 12 stands for a twelve inch rise for every twelve inch run; and the mark 6 stands for a six inch rise for every twelve inch run.

Assume that the carpenter wants to cut a jack rafter for a siX inch rise. He places the arm B at the mark 6 on the quadrant and then tightens the butterfly nut If). He then opens the arm [9 or 20, depending on whether he is to cut a right or left hand rafter and then places the device on the jack rafter D. Figure 1 shows the arm 20 extended. The carpenter places the device on the rafter top so that the underside of the pivot pin [4 rests on the rafter top and the head 3 also rests on the rafter top. It will be noted from Figure 4 that the bottom of the head 3 lies flush with the bottom of the body A and projects beyond the sides of the body A as shown at 21 in Figure 4. In using the instrument, one of the portions 21 rests on the rafter top.

The instrument as shown in Figure 1 is set for making the rise line 28 extend at right angles to the rafter top 24. This will cause the side bevel line 29 to extend at about 45 to the plane of the rafter side 25. The drawing shows the instrument backed away slightly from the drawn lines 28 and 29. The broken lines 30 .and 3| indicate the rise angle and the .side'bevel angle- Since the arm 20 is pivoted to the head 3, it will swing down to contact with the rafter top 24 regardless of the angle assumed by the base A on the rafter side 25.

It will be seen from this that regardless ofthe angular position made by the body A on the rafter side, the arm 20, when brought into contact with the rafter top, will extend at the required angle. The carpenter can draw two lines on the rafter corresponding to the angles of the body A and the'arm 20 and then cut the rafter along the drawn lines. The cut piece X is discarded and the cut end of the rafter will now fit the hip rafter, as indicated in Figure 5. When jack rafters on the opposite side of the hip rafter are to be cut, the arm I9 is used in place of the arm 20.

After the device has been used it may be folded as shown and is ready for any subsequent use. The device is small enough when folded to be carried in the pocket. When the arm I 9 is used, the opposite end of the shaft I4 is used to rest the device on the rafter top. The arms l9 and 20 are at a 45 angle to the undersurface of the base A at all times. The arms I9 and 20 swing in planes that extend at angles of with respect to the plane in which the arm B swings. The markings 26 on the quadrant 2 take into account that the device is supported on the rafter D by the pivot pin l4 and the edge 21 of the head 3. This dispose the arm B at an angle with respect to the rafter top, but this angle has been taken intoconsideration in. thedesigning of the instrument so that the body A and either. the arms l9- or 20 will extend 'at the proper angles on the rafter when the arm B has been set at the desired angle indicated by the marking 26 and. the instrument has been placed on the rafter in the manner illustrated and described. When the body A is adjusted to the pitch of. the roof, the arm 20 is self adjusting to the side out on the jack rafter. The arm 2|] therefore automatically assumes the proper angle for the side cut.

I claim:

1. A jack rafter bevel square comprising an elongated body having ahead at one end and a quadrant placed close to the head whose plane extends at right angles to the plane of the body, an arm pivotally secured to the quadrant, means for securing the arm in different angular positions, an abutment carried by the outer end of the arm, said abutment and head adapted to rest on' a jack rafter in a position-to permit the elongated body to lie against the side of the rafter, and. a second arm pivoted. to the head and swingable in a plane that extends at an angle of 135 to the plane in which the first arm swings.

2. In a jack rafter bevel square, an elongated body having a fiat undersurface constituting a ruling edge for guiding a pencil when marking a rafter, a pair of arms pivoted to the body so as to swing in planes that are at right angles to each other and make an angle of 45 to a plane that is perpendicular to the body undersurface and extends parallel to the length of the body, and means for supporting the device on a rafter in a predetermined manner so that the body will indicate the angle of the rise'cut to be made on the rafter side and one of the arms will contact with the rafter top and indicate the angle of the side bevel cut to-be 'made'on the rafter top'.;

3. A jaekrafter bevel square comprising'an elongated body having a flat undersurface; an arm pivotally mounted on the body top and near I one end of the body, said arm being swingable in a plane that parallels the lengthof the 'body and that lies perpendicular to the body undersurface, a pivot pin carried by the outer end of the arm and designed to rest on a'rafter top, a

head secured to the end of the body that'lies closest to the pivot point of'the arm,1and acting as a second support for the device; arms pivoted to the head and being swingable in place that extend at right angles to each other and are at angles of 135 with respect to the plane in which the first arm swings, an arcuate scale associated with the first arm for indicating various rafter I pitches, and means for securing the first arm in the desired angular position, whereby a placing of the device on a rafter so that the pivot pin and head will be supported by the rafter top, the body and one of the second-named arms that extends over the rafter top will indicate the proper angles for the rise cut and side bevel cut on the rafter.

4. A jack rafter bevel square comprising an elongated body with a fiat undersurface and a centrally disposed and longitudinally extending central rib disposed on top of the body, an inverted V-shaped head disposed on the body top and at one end, the sides of the head extending beyond the body sides and lying flush with the body under-surface, two semi-circular discs arranged on each side of the rib and having arcuate slots extending through 90, an arm pivoted between the discs, a bolt carried by the arm and slidable in the arcuate slots, a butterfly nut for securing the arm in adjusted position, a pivot pin mounted at the free end of the arm and adapted to rest on a rafter top, auxiliary arms pivoted to the head and swingable in planes that extend at right angles to each other and make angles of 135 to the plane in which the first mentioned arm swings,-either one of said auxiliary arms cooperating with the body to constitute guide edges for marking instrument, whereby the angle of the rise cut and the angle of the side bevel out can be marked on the side and top of a rafter on which the device is placed and supported, with the pivot pin and head resting on the rafter top.

PHILANDER F. WITTER. 

